The invention relates generally to a control apparatus for internal combustion engines, and, in particular, to a control apparatus for controlling fuel supplied to an internal combustion engine in accordance with induced air pressure.
Known control apparatus of this type (German Offenlegungsschrift No. 27 31 107) function in accordance with the charge air pressure in the intake manifold of the engine. With an adjustment member which can be subjected to the charge air pressure via a pressure chamber, they either engage the control linkage in order to adapt the controller characteristic curve appropriately to the varying charge air pressure or, as a charge pressure dependent full-load stop, they limit the full-load position permissible at a particular time of the supply quantity adjustment member of the fuel metering apparatus. In these apparatuses, the charge air pressure is utilized as a standard for the quantity of air supplied and it acts on the final control element via an adjustment diaphragm serving as a movable wall and displaceable against the force of a restoring spring. The counterpart pressure chamber located opposite the pressure chamber subjected to the charge air pressure is subjected to atmospheric air pressure and thus this diaphragm-type adjustment member can measure only the difference between the charge air pressure and the atmospheric pressure. This, however, is well known to result in an imprecise air mass signal and thus it falsifies the charge pressure dependent correction of the injection quantity. In order to eliminate this disadvantage, control apparatuses are known (German Auslegeschrift No. 24 48 656) in which an evacuated diaphragm box is used as the restoring means instead of restoring springs, such diaphragm boxes being of the kind also used in correction apparatuses dependent on atmospheric pressure. These diaphragm boxes, if they are additionally supplied with a temperature correction as well, furnish a precise air mass signal; however, in disadvantageous fashion, they have only limited capacity and cannot be highly stressed mechanically; thus they are not suited for use in charge pressure dependent full-load stops which are subjected to severe changes in load and to temperature stresses and which must perform long adjustment strokes rapidly.